Multiple diode lasers positioned adjacent to each other on a common semiconductor substrate (laser array) can function as the light source in various optical systems. For example, a wideband optical disk recorder could be constructed in which each diode of a laser array is used to write one data track on the optical disk. If the laser array has N lasers, then the required bandwidth for each track is reduced by a factor of 1/N, thus providing an extremely attractive wideband system.
In the exemplary case of a wideband optical disk recorder, data track spacing on the order of 0.002 mm is desired. Currently available semiconductor technology can provide a laser array with a laser spacing limit, due, in part, to thermal interaction effects, of only about 0.25 mm. The light beams provided by such an array would have a large divergence angle. Because the spacing of the lasers from each other is substantially larger than the desired track, or beam spot, spacing at the optical disk, the laser array must be located at a substantial distance from the focusing objective lens of the system to provide enough demagnification to provide the proper beam spot spacing. The substantial distance between the laser array and the objective lens, and the large divergence angle of the emitted light beams, causes the amount of light collected by the objective lens to be very small, that is, a significant amount of beam power is lost, making such systems impractical.